We will study the conduction system by serial section in cases of sudden death and in cases where His bundle recordings have been done. We will study the course of conduction system in surgically important types of congenital heart disease. We will study the conduction system in acromegaly and asymmetrical septal hypertrophy to find out whether conductive cells hypertrophy. We will continue our studies of the conduction system and the A-V communications in congenital A-V block and WPW. We will study the myocardium in congenital heart disease by strategic sections of inflow, outflow, tracts and the septum. We will continue to examine grossly most of the congenital hearts in the Chicago area. We will probe the following complexes grossly--fetal coarctation, mitral atresia with ventricular septal defect, and coarctation with ventricular septal defect.